The present invention relates to a vehicle driving assistance system for enhancing the safety of a vehicle by executing alarming, automatic braking and automatic steering according to environment ahead of the vehicle.
In recent years, various techniques have been developed for vehicles in which a driving environment ahead of a vehicle is detected by a camera, a laser radar system and the like which are installed on the vehicle to thereby recognize obstacles and preceding vehicles from the driving environment data so detected, so as to enhance the safety of the vehicle by executing alarming, automatic braking and automatic steering.
For example, JP-A-5-52608 discloses a technique in which riskinesses on a plurality of risk factors are calculated based on external environmental conditions, how the driver is controlling the vehicle and running conditions of the moving vehicle, a degree of emergency is calculated which is an estimated value of time required from the current point in time until the riskiness reaches a predetermined limit value, the respective risk factors are put in order of priority based on their degrees of emergency, and certain operations are performed on some of the risk factors in order of priority within a time allowance for avoiding the risk factor put in the first place in the order of priority.
In addition, JP-A-10-211886 discloses a technique in which obstacles are detected by a plurality of radars provided on the periphery of a vehicle, and a potential riskiness then is obtained based on information on a relative moving state which is made up of respective azimuthal angles, relative speeds and distances of the plurality of obstacles so detected, and a steering control is performed on the potential riskiness so obtained.
Furthermore, JP-A-2004-362227 discloses a technique in which a vehicle condition of a subject vehicle and a driving environment of the subject vehicle are detected, a risk potential is set based on a collision allowance time and an inter-vehicle time, and an acceleration pedal reaction force is controlled based on the risk potential so set.
However, in the technique disclosed in JP-A-5-52608, a limitation is imposed on the order of priority that can be taken into account, and there is a fear that an avoidance control with good accuracy cannot be performed over a long period of time. In addition, in the technique disclosed in JP-A-10-211886, a risk distribution in a two-dimensional plate needs to be treated in three-dimension, this causing a problem that the quantity of operation is increased. In addition, since the plurality of radars or the like need to be provided on the periphery of the vehicle, a problem arises that spaces necessary for provision of the plurality of radars have to be secured. Furthermore, in the technique disclosed in JP-A-2004-362227, depending upon types (attributes) of target objects, there occurs a case where a high risk is set unnecessarily, for example, for an electric-light pole on the shoulder of the road or a low risk is set for a pedestrian whose future movement is difficult to be estimated, this resulting in a problem that the risk potential cannot be set with good accuracy.